1. Field of the Invention
The present invention relates to a grinding method and a grinding machine for grinding a workpiece with a rotating grinding wheel, and more particularly to an environmentally-friendly grinding method and machine which can reduce the consumption of energy from start to end of workpiece grinding operation.
2. Description of the Related Art
Conventionally, there has been known a grinding machine in which a wheel head that rotatably supports a grinding wheel in a cantilever fashion by means of static bearings is mounted on a bed via a slide mechanism such that the wheel head can be advanced toward and retreated from a workpiece rotatably supported between a spindle head and a tailstook (see, for example, Japanese Patent Application Laid-Open (kokai) Nos. H10-118922 and 2001-82473. In such a grinding machine, the workpiece is ground with the grinding wheel, while coolant is fed from a coolant nozzle toward a grinding zone between the grinding wheel and the workpiece.
Specifically, Japanese Patent Application Laid-Open No. H10-118922 discloses a grinding machine in which a wheel head is slidably guided along a pair of guides provided on a bed, and which includes a feed mechanism which transmits rotational torque of a servomotor fixed to the bed to the wheel head via a ball-screw mechanism so as to advance and retreat the wheel head. A grinding wheel is rotatably supported on the wheel head in a cantilever fashion via static bearings.
Japanese Patent Application Laid-Open No. 2001-82473 discloses a grinding machine in which lubrication oil supplied to bearing portions is caused to flow from oil discharge grooves to an oil reservoir portion for temporary accumulation and then flow out toward a lubrication oil supply apparatus via a drain port.
In conventional grinding machines, since a grinding wheel is rotatably supported on a wheel head in a cantilever fashion via static bearings, the shaft of the grinding wheel and bearing portions thereof are designed to have large diameters in order to increase rigidity during grinding operation, to thereby secure machining accuracy.
Further, the bearing portions are supported by means of static bearings, and lubrication oil supplied to the bearing portions is caused to flow from oil discharge grooves to an oil reservoir portion for temporary accumulation and then flow out toward a lubrication oil supply apparatus via a drain port. Therefore, the above-mentioned oil reservoir portion is provided on the wheel head, which is a movable section.
However, in the conventional grinding machines, since the shaft of the grinding wheel and the bearing portions thereof have large diameters and the oil reservoir portion is provided on the wheel head, the weight of the movable section is large, which makes it difficult to move the movable section at high speed or to move the movable section at large acceleration.
In other words, since the movable section is moved at low speed and low acceleration in order to render the consumed power at the time of indexing the grinding wheel smaller than that at the time of grinding a workpiece, the time required to index the grinding wheel, and thus, the time required to machine the workpiece cannot be shortened, so that the quantity of consumed energy cannot be reduced.